Large water leg boiler

ABSTRACT

This application covers a wet base boiler of the multi-section type, that is, a boiler in which the firebox is &#39;&#39;&#39;&#39;surrounded&#39;&#39;&#39;&#39; by water, but one of the legs of each section, i.e., the right leg, is made different in cross-sectional area from the left leg. Thus, the right legs may be made much larger in cross-sectional dimensions than the left legs, especially if the nipple port of the boiler is positioned above the right legs. This results in an improved quality of steam for boilers operated to generate steam. A tankless water coil may be added to the boiler, either positioned in the water chamber above the firebox or in the nipple port area. In either case, there will be a clockwise water movement throughout the sections of the boiler due to the difference in the sizes of the right and left legs, causing the water to move downwardly in all of the right legs and to move upwardly in all of the left legs. This circuital travel of the water through the legs of the various sections improves the heat transfer to the water flowing through the tankless coil.

United States Patent 11 1 Peterson Mar. 12, 1974 [73] Assignee: American Standard Inc., New York,

[22] Filed: Apr. 11, 1973 [21] Appl. No.: 350,221

France 122/225 Primary Examinerl(enneth W. Sprague v Attorney, Agent, or Firm-Jefferson Ehrlich; Robert G. Crooks [5 7] ABSTRACT This application covers a wet base boiler of the multisection type, that is, a boiler in which the firebox is surrounded by water, but one of the legs of each section, i.e., the right leg, is made different in crosssectional area from the left leg. Thus, the right legs may be made much larger in cross-sectional dimensions than the left legs, especially if the nipple port of the boiler is positioned above the right legs. This results in an improved quality of steam for boilers operated to generate steam. A tankless water coil may be added to the boiler, either positioned in the water chamber above the firebox or in the nipple port area. In either case, therewill be a clockwise water movement throughout the sections of theboiler due to the difference in the sizes of the right and left legs, causing the water to move downwardly in all of the right legs and to move upwardly in all of the left legs. This circuital travel of the water through the legs of the various sections improves the heat transfer to the water flowing through the tankless coil.

21 Claims, SDI-sawing Figure;

PATENTEMR 12 I974 SHEET 2 OF 2 FEG.3

FIG.5

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LARGE WATER LEG BOILER This application relates generally to boilers and, more particularly, to boilers of the wet base type, that is, boilers embodying a firebox which feeds heat to water contained in interconnected conduits or other passages forming a basal leg and right and left side legs of the firebox and a compartment above the firebox.

One of the principal objects of this invention is to improve the operation of a wet base type of boiler and to increase its efficiency. I

Another of the principal objects of this invention is to simplify the construction and improve the operating efficiency of a wet base boiler and improve its heat generating capacity per unit of fuel used while reducing the cost of production of such a boiler construction.

In US. Pat. No. 3,554,167, issued .Ian. 12, 1971, to A. E. Martin et al., assigned to the same assignee as the present application, there is described a form of wet base boiler having fluidically interconnected sections each including right and left water legs on corresponding sides of the firebox, a basal water leg positioned beneath the firebox and a water chamber segment or leg joining the upper ends of the right and left legs and positioned above the firebox. The right and left legs are of the same cross-sectional dimensions and of the same length, but a refractory plate or plates are inserted within the firebox against one of the side walls of the firebox, i.e., the right wall, which serve to delay the transfer of heat from the firebox to the water within the right legs without affecting the transfer of heat to the water of the left legs or the basal legs. By this construction, the delay in the transfer of heat to the right legs renders the water in the right legs at a temperature which is somewhat lower than that within the left legs. Hence, the water in the left legs rises due to its higher temperature, while the water in the right legs descends. This may be regarded as a thermal pump effect, driving the water in the boiler into a circuitous path. The water thus rises in each left leg, then travels to the right in the upper water chamber, then travels downwardly in each right leg and then moves to the left in each basal leg. This clockwise circulation is repeated again and again, thereby improving the operating efficiency of the boiler.

However, the insertion of the refractory plate or plates against one of the side walls of the firebox substantially reduces heat transver in the firebox. Furthermore, the refractory plates are removable and sometimes become chipped or broken during removal or after installation and use, thereby increasing the breakage hazards and reducing the life of the construction. In addition, refractory plates are costly and, aside from the inherent reduction in heat transfer introduced by such plates, they are also subject to breakage in shipment and during storage. They also reduce the effective heating space within the firebox. The invention of the present application overcomes these problems by eliminating the refractory plates.

According to the present invention, one of the two legs of each section of the wet base boiler is made much larger in cross-section than that of the other leg. The leg selected for enlargement is preferably the leg positioned beneath the steam discharge port or nipple port, as it is sometimes called. Thus, if the nipple port is located in the upper right hand corner of the boiler, the right leg of each section will be preferably enlarged to increase its water volumetric capacity according to the invention, while the left leg of each section will be unchanged in size or perhaps reduced somewhat in size.

This mere change in dimensions of one of the legs of each section introduces a significant improvement in the quality of the steam generated in a boiler used for supplying steam.

If a Wet base boiler having a large leg under its nipple port is also equipped with a so-called tankless heating coil which may be positioned in the nipple port or in the so-called steam chest adjacent to and perpendicular to the nipple port near the top of the boiler, an improvement in the heat transfer property of the boiler will be achieved. The heat extracted by the tankless coil to raise the temperature of the water in the tankless coil will aid in moving the water in the right leg of each section in a downward direction because of its lower temperature and the water in the left leg of each section in an upward direction. This circulatory or clockwise motion will be repeated again and again and it significantly improves the overall efficiency of the boiler operation.

This same improved water circulation is obtained from a hot water boiler equipped with a tankless coil and having a larger leg on one side, i.e., the right side, of each boiler section.

This invention, together with its further objects and features, will be better and more clearly understood from the more detailed description and explanation hereinafter following when read in connection with the accompanying drawing in which:

FIG. 1 shows a cross-sectional view of a wet base steam boiler when cut along a line mid-way between the right and left side walls of the boiler;

FIG. 2 illustrates a front elevational view, in crosssection, of a wet base water boiler of this invention equipped with a tankless coil and viewed from the front face of the boiler;

FIG. 3 shows a schematic representation of the wet base boiler illustrating the path of water traveling through the water sections and compartment of the boiler where the right legs of the sections are larger than the left legs and the boiler is equipped with a tankless coil;

FIG. 4 shows a cross-sectional view of one of the sections of the boiler taken along the line 44 of FIG. 3; and

FIG. 5 illustrates a portion of a boiler employed for steam production, but excluding a coil for separately heating domestic water.

The same or similar reference characters will be employed throughout the drawing to represent the same or similar parts whenever they may occur throughout the drawing.

Referring to the drawing, for example, FIGS. 1 and 3, there will be seen a fluidically interconnected multisectional boiler of the wet base type, each section in cluding a right leg RL, a basal leg BL, a left leg LL and a water chamber segment WC. As shown for illustration in FIG. 1, the boiler may include five similar intermediate sections and two end sections. The firebox is designated FE and, as seen in FIGS. 1, 2 and 3 of the drawing, the firebox FB is positioned within the four fluidically interconnected segments of each section of the boiler, namely sections RL, BL, LL and WC. The water chamber segments WC above firebox FB interconnect all of the sections through the composited nipple port NP. The nipple port designated NP may be in the upper right-hand corner of the boiler, as shown, extending from about the front of the boiler to about the rear of the boiler. The nipple port NP is in communication with the upper chamber segments WC so as to receive the heated water or the generated steam, as the case may be for a water or steam boiler. A tankless water heater TH may, if desired, be mounted within the water compartment WC of the boiler, as shown in FIG. 2, for separately heating water in the conventional manner. If desired, the tankless water heater TH may be mounted within the nipple port NP, as shown in FIG. 3. A fuel burner is shown in FIG. 1 and is designated BU. The construction of the fuel burner need not be explained because it is well known.

It will be noted that the right leg RL of each section is substantially equal in length to the left leg LL, but the cross-sectional dimensions of the right leg RL are much larger than those of the left leg LL of each section, as seen in FIG. 4. For example, both legs RL and LL of each section may be substantially rectangular in crosssection, but the cross-sectional area of the right leg RL may be, perhaps, twice as great, or even greater, than the area of the left leg LL. The basal leg BL of each section of the boiler fluidically interconnects the right leg RL and the left leg LL of each section to allow water to flow between the two interconnected legs. The nipple port NP is in direct communication with the water compartment segments WC, as already noted, and hence fluidically interconnects all of the right legs RL and all of the left legs LL of the several sections and may be regarded as a connecting reservoir for the water to be heated by the boiler or for the steam to be derived from the heated water in steam chest SC. The employment of a basal water leg BL beneath the firebox FB, because it is exposed to the heat of the firebox FB, greatly improves the heat absorbing property of the circulating water. The boiler may be employed for hot water production or for steam production, as may be desired, and the hot water or steam, whichever it may be, will be delivered from the water chamber segments WC or steam chest SC to, and discharged through, the nipple port NP which is common to all of the sections and interconnects all sections.

By virtue of the marked differences in the crosssections of the right and left legs RL and LL, respectively, the volumetric water capacity of each right leg will be much larger than that of each left leg. By reason of the significant difference in the volumetric water capacities of the two legs of each section, and assuming a uniform fire temperature in the firebox FB, heat will be transferred to the fluid in the left leg at a rate which will be significantly different from the rate of heat transfer to the right leg. Indeed the rate at which heat is transferred to the right leg is higher than the heat transfer rate to the left leg, and this difference is due to, and proportional to, the differences in the dimensions of the two legs, as already observed. The rate of heat transfer to the two legs is unequal whether measured in terms of BTUH per pound of fluid within the legs or measured in terms of the cross-sectional areas of the legs. It is this unequal rate of heat transfer per unit of the weight or the volume of the fuel, or the crosssectional area of the two dissimilar legs, that produces the desired effects of this invention.

In a steam boiler, such as that shown in FIG, 5, steam collects above the water level WL in steam chest SC as the temperature of the water reaches the boiling temperature. The generated steam travels over the surface of the water through the nipples of the several sections at a velocity which depends upon the height of the water line WL as well as on the rate at which steam is generated. Thus, as the water line WL rises, the velocity will increase due to the reduction in the space through which the steam must flow, and vice versa, and, as the steaming rate increases, the velocity will increase, and vice versa. If the steaming rate increases, there will also be an increased steam bubble formation, and the increased bubble formation will act to raise the water line WL. The water line WL will rise as additional bubbles develop because the water volume and the bubble volume combine. This combination cuts down the open space above the combination through which the steam is required to travel in leaving the boiler. The steam bubble formation may be greater in one area than in other areas.

The steam bubble concentration will be less in the right leg RL of each section because of its greater cross-sectional area than the bubble concentration will be in the left leg LL. Consequently, because the nipple ports NP of the several sections are positioned above all of the right legs, the water level at and near the nipple ports NP will be less disturbed than it will be above the left legs LL. This, therefore, reduces the percentage of water picked up by the traveling steam as it exits to and through the nipple ports NP. Thus, the steam quality will be improved. This is an important improvement.

Thus, by enlarging the cross-sectional dimensions of the right legs, improved steam quality is effected.

It will be observed that, in FIG. 2, a tankless heater coil TH is embodied in the water chamber WC across the water chamber extending from the left side of the steam boiler to the right side of the boiler. In this steam boiler, the heat of the firebox PE is used to develop steam to be supplied, for example, to heat the interior space of a building, but the coil TH transports water to be heated separately and to be supplied by the boiler for other purposes. As cold water reaches coil TH, it absorbs heat from the hot water in the water chamber WC. The cold water, in traveling from left to right and absorbing heat from the water within chamber segments WC, cools the water within chamber segments WC. The water within the chamber segments WC that is relatively cooled becomes more dense and drops. The dense water, therefore, flows into the right legs RL of the various sections.

The increased density of the water flowing into the right legs RL from the water chamber segments WC is accompanied by the relatively higher temperature of the water in the left legs LL. This creates what may be regarded as a form of heat pump which acts so as to drive the water within each section into a circulatory or clockwise path around the firebox FB of the boiler. That is, the water in the left legs LL will move upwardly, while the slower rising temperature or lower temperature of the water in the right legs RL will cause the water in the right legs RL to change direction and move downwardly. The path of the water may then be traced as traveling in a downward direction in all of the right legs RL, then to the left in all of the basal legs BL, then upwardly through all of the left legs LL, and then to the right through the water chamber segments WC. This clockwise circulation will be continued and repeated. As heat is absorbed by the water raised in temperature as it flows through and out of the heater coil TH, the temperature of the fluid in the water chamber segments WC will drop. The drop in temperature s'oon interrupts the production of steam within the boiler and this interruption will continue until the transfer of heat to the water within coil TH ceases ordrops to a substantially lower rate.

In the arrangement shown in FIG. 3 in which the tankless heater coil TH is positioned within the nipple port NP, there will be a similar cooling effect on the water within the water chamber segments WC adjacent to the tankless heater TH as cold water flows into and through the heater TH and is heated by the hot water within chamber segments WC. Thus, as in the case of the FIG. 2 arrangement, which embodies a differently located tankless heater TH, the cooling effect developed in heating the water within the heater TH results in an increased density of the water within chamber segments WC at the right side of the boiler. Hence, the cold water will move downwardly through the various right legs RL of the several sections, while the water in the left legs LL will move upwardly. A similar circulatory or clockwise movement of water within the boiler of FIG. 3 will be developed in that arrangement.

' The boilers of the type shown in FIGS. 2 and 3 may be used to produce hot water for so-called space heating or for producing steam for space heating or for other purposes. In any case, the water of elevated temperature, or the steam, as the case may be, will be driven through the nipple port NP to supply the building or other structure where the heated fluid medium is to be utilized, for example, for heating the building. All four legs RL, BL, LL and WC of the several sections will be active in moving the water to be heated in a continuous path in, for example, the clockwise direction and, at the same time, heat will be transferred from the flaming gases of the firebox F8 to all four legs. Because of the addition of the tankless heater coils TH to the boilers of FIGS. 2 and 3, hot water will be also made available for separate use, as may be desired.

Thus, by increasing the dimensions of one of the legs of each section, for instance, the right legs RL, two effects will be coordinated to improve the efficiency of a boiler, firstly, the effect of increasing the surface area of the water at the top of the right legs RL to diminish the bubble formation in the region of the nipple port NP during steam boiler operation and, secondly, a relative lowering of the temperature ofthe water reaching the right legs RL so as to introduce the circulatory or clockwise rotation of the water around the firebox FB in all of the sections during tankless operation in steam or hot water boilers. Steam quality (namely dryness), noise reduction, fuel consumption and general overall efficiency of the boiler are concomitantly developed.

In a steam or hot water boiler equipped with a tankless hot water coil TH as exemplified by FIGS. 2 and 3, the boiler will operate to generate steam or hot water, as the case may be, for space heating or for other purposes, and the operation will be fully effective as long as no water, or substantially very little water, passes through and is heated in the hot water coil TH. As already indicated, when the steam boiler generates steam, the quality of the steam (i.e., its dryness) will be improved due to the leg size changes-illustrated and described in accordance with this invention. However, when the hot water coil TH delivers a substantial quantity of hot water, the density of the water within the water chamber WC of a steam or hot water boiler will increase as already noted supra. The transfer of heat to the water within the hot water coil TH will cause the temperature of the water within each chamber WC to drop. If the boiler is a steam producer, the production of steam willcease. If the boiler is a hot water boiler, the drop in temperature will cause the controls to shut off the flow of hot water to the spaces to be heated. For both steam and water boilers, the drop in boiler water temperature in chamber segments WC causes the controls to turn on the fuel burner to maintain or raise the temperature of the boiler water. If, and only if, the temperature of the water within the steam or water boiler rises sufficiently, the controls will then allow energy to flow to the spaces to be heated during the time that water is being drawn from the tankless heater water coil TH.

The cross-sectional shapes of the two legs RL and LL of each section, although shown in FIG. 4 and described as preferably somewhat rectangular, may be of any other shape, such as circular, elliptical, etc., to achieve the same or equivalent results. Furthermore, the cross-sectional dimensions of the two legs of each section may be proportioned and fixed at any desired ratio consistent with the other parameters of the boiler,

but all of the right legs RL should bear substantially about the same area ratio to that of the corresponding left legs LL of the several sections.

It will be observed that the firebox FB has substantially no fire-plate or other obstruction therein. All of the heat generated by the burning fuel within the firebox is directly applied to the four segments of each section. This is an important structural improvement. It is a distinct improvement over the arrangement of the type shown in the aforementioned Pat. No. 3,554,167.

If desired, the several sections of the boiler may be sealed gas-tight so as to be usable under forced draft. The seal may be achieved by grooving one or both of the mating endwalls of. each pair of adjacent sections and inserting a sealant therein, as shown and described in US. Pat. No. 3,533,379 to E. A. Martin et al., issued Oct. 13, l97Q and assigned to the same assignee as the present application.

While this invention has been shown and described in certain arrangements and proportions merely for illustration and explanation, it will be readily apparent that the arrangements may be embodied in various forms and proportions, all within the scope of this invention.

What is claimed is:

l. A boiler comprising a plurality of adjacent sections to be filled with water, each section including two side legs and a basal leg fluidically interconnecting the bottoms of the side legs, one of the side legs of each section being substantially larger in cross-section than that of the opposite side leg, a firebox bounded by said side legs and said basal legs, a compartment positioned above the firebox and fluidically connected to the side legs of said sections and to be partially or substantially completely filled with water, the heat emanating from the firebox to be directly supplied to said side legs and said basal legs and to the compartment.

2. A boiler according to claim 1 having an upper nipple port near the top of the compartment and positioned on that side-of the boiler which is adjacent to the legs having the larger cross-sectional areas.

3. A boiler according to claim 2 having a separate water heater coil mounted within the boiler for heating water separately transmitted through said coil.

4. A wet base boiler having a plurality of closely adjacent sections each having oppositely positioned side legs, a basal leg interconnecting the bottoms of the side legs and an upper compartment, a nipple port region common to all of said sections and interconnected with the upper open ends of said side legs, a common firing space mounted between said side legs and also between the basal legs and said upper compartments and supplying heat to all of said sections and said compartments, one of the said legs of each section being substantially larger in its cross-sectional dimensions than the opposite side leg, whereby water supplied to the boiler and heated by the firebox will circulate continuously through all of the legs and the compartment in a path in which the water in the side legs of larger dimensions flows downwardly while the water in the smaller side legs moves upwardly.

5. A wet base boiler according to claim 4 in which the nipple port region is provided above the larger legs to receive the heated water of each compartment and any accompanying steam derived from the heated water.

6. A wet base boiler according to claim 5 including a water heater coil within the boiler for transmitting water which is supplied separately from the water traveling through the side legs of the sections.

7. A wet base-boiler according to claim 6 in which the side legs are of substantially rectangular cross-section.

8. A wet base boiler having a plurality of adjacent sections each of which includes two substantially parallel side legs of different crosssectional dimensions, a basal leg interconnecting the side legs so that water may fill the sections and a compartment, a firebox seated on the basal legs of said sections, the compartments being positioned above the firebox and connected to the side legs of the sections so that water in either of said side legs may flow to the compartment and water in the compartment may flow to either of the side legs, means for determining the directivity of the water flow through the sections, the direction of water flow being downwardly in the side legs of the larger cross-section and upwardly in the side legs of smaller cross-section.

9. A wet base boiler according to claim 8 including a tankless hot water coil through which water may be independently transmitted, Said coil being mounted within the boiler so as to be heated .by the water in the compartments.

10. A wet base boiler according to claim 9 in which the side legs have substantially rectangular crosssections. I

11. A wet base boiler according to claim 10 in which a nipple port is formed in the compartments above the side legs of larger cross-section.

12. A wet base boiler having a plurality of adjacent coupled sections heated from a common source of heat, and means for controlling the directivity of water flow through said sections, the legs on one side of each of the sections being larger in cross-section than those on the other side of each section, whereby water to be heated will flow downwardly through the larger legs and upwardly through the smaller legs.

13. A wet base boiler according to claim 12 having a tankless water heating coil mounted in the boiler and heated by water traversing said sections.

14. A wet base boiler according to claim 13 having a nipple port positioned substantially vertically above the legs of the sections having the larger cross-sections.

15. A wet base boiler according to claim 14 in which the cross-section of the legs are substantially rectangular.

16. A wet base boiler having a plurality of adjacent coupled sections and a water compartment above said sections so arranged that said sections and said compartment may be heated from a common source of heat, a tankless hot water coil to be heated by the water in said compartment, and means for controlling the directivity of water flow through said sections, the legs on one side of each of the sections being larger in volumetric capacity than those on the other side of each section, whereby water to be heated will fiow downwardly through the larger legs and upwardly through the smaller legs.

17. A wet base boiler according to claim 16 having a nipple port positioned substantially vertically above the legs of the sections having the larger volumetric capacity.

18. A wet base boiler according to claim 17 in which the cross-section of the legs are substantially rectangular.

19. A boiler comprising a plurality of adjacent coupled sections to be filled with water, each section including two side legs and a basal leg fluidically interconnecting the bottoms of the side legs, one of the side legs of each section being substantially larger in volumetric capacity than that of the opposite side leg, a firebox-bounded by said side legs and said basal legs, a compartment for each section which is positioned above the firebox and fluidically connected to the side legs of said sections and to be partially or substantially completely filled with water, a tankless water heater coil heated by water in said compartment, a nipple port mounted in said boiler above the larger side legs, the heat emanating from the firebox to be directly supplied to said side legs and said basal legs and to the compartments and causing the water in the legs having the larger capacity to move downwardly while the water in the opposite legs moves upwardly.

20. A boiler according to claim 19 in which the tankless water heater coil is mounted in said compartments.

21. A boiler according to claim 19 in which the tankless water heater coil is mounted in the nipple port. 

1. A boiler comprising a plurality of adjacent sections to be filled with water, each section including two side legs and a basal leg fluidically interconnecting the bottoms of the side legs, one of the side legs of each section being substantially larger in cross-section than that of the opposite side leg, a firebox bounded by said side legs and said basal legs, a compartment positioned above the firebox and fluidically connected to the side legs of said sections and to be partially or substantially completely filled with water, the heat emanating from the firebox to be directly supplied to said side legs and said basal legs and to the compartment.
 2. A boiler according to claim 1 having an upper nipple port near the top of the compartment and positioned on that side of the boiler which is adjacent to the legs having the larger cross-sectional areas.
 3. A boiler according to claim 2 having a separate water heater coil mounted within the boiler for heating water separately transmitted through said coil.
 4. A wet base boiler having a plurality of closely adjacent sections each having oppositely positioned side legs, a basal leg interconnecting the bottoms of the side legs and an upper compartment, a nipple port region common to all of said sections and interconnected with the upper open ends of said side legs, a common firing space mounted between said side legs and also between the basal legs and said upper compartments and supplying heat to all of said sections and said compartments, one of the said legs of each section being substantially larger in its cross-sectional dimensions than the opposite side leg, whereby water supplied to the boiler and heated by the firebox will circulate continuously through all of the legs and the compartment in a path in which the water in the side legs of larger dimensions flows downwardly while the water in the smaller side legs moves Upwardly.
 5. A wet base boiler according to claim 4 in which the nipple port region is provided above the larger legs to receive the heated water of each compartment and any accompanying steam derived from the heated water.
 6. A wet base boiler according to claim 5 including a water heater coil within the boiler for transmitting water which is supplied separately from the water traveling through the side legs of the sections.
 7. A wet base boiler according to claim 6 in which the side legs are of substantially rectangular cross-section.
 8. A wet base boiler having a plurality of adjacent sections each of which includes two substantially parallel side legs of different cross-sectional dimensions, a basal leg interconnecting the side legs so that water may fill the sections and a compartment, a firebox seated on the basal legs of said sections, the compartments being positioned above the firebox and connected to the side legs of the sections so that water in either of said side legs may flow to the compartment and water in the compartment may flow to either of the side legs, means for determining the directivity of the water flow through the sections, the direction of water flow being downwardly in the side legs of the larger cross-section and upwardly in the side legs of smaller cross-section.
 9. A wet base boiler according to claim 8 including a tankless hot water coil through which water may be independently transmitted, said coil being mounted within the boiler so as to be heated by the water in the compartments.
 10. A wet base boiler according to claim 9 in which the side legs have substantially rectangular cross-sections.
 11. A wet base boiler according to claim 10 in which a nipple port is formed in the compartments above the side legs of larger cross-section.
 12. A wet base boiler having a plurality of adjacent coupled sections heated from a common source of heat, and means for controlling the directivity of water flow through said sections, the legs on one side of each of the sections being larger in cross-section than those on the other side of each section, whereby water to be heated will flow downwardly through the larger legs and upwardly through the smaller legs.
 13. A wet base boiler according to claim 12 having a tankless water heating coil mounted in the boiler and heated by water traversing said sections.
 14. A wet base boiler according to claim 13 having a nipple port positioned substantially vertically above the legs of the sections having the larger cross-sections.
 15. A wet base boiler according to claim 14 in which the cross-section of the legs are substantially rectangular.
 16. A wet base boiler having a plurality of adjacent coupled sections and a water compartment above said sections so arranged that said sections and said compartment may be heated from a common source of heat, a tankless hot water coil to be heated by the water in said compartment, and means for controlling the directivity of water flow through said sections, the legs on one side of each of the sections being larger in volumetric capacity than those on the other side of each section, whereby water to be heated will flow downwardly through the larger legs and upwardly through the smaller legs.
 17. A wet base boiler according to claim 16 having a nipple port positioned substantially vertically above the legs of the sections having the larger volumetric capacity.
 18. A wet base boiler according to claim 17 in which the cross-section of the legs are substantially rectangular.
 19. A boiler comprising a plurality of adjacent coupled sections to be filled with water, each section including two side legs and a basal leg fluidically interconnecting the bottoms of the side legs, one of the side legs of each section being substantially larger in volumetric capacity than that of the opposite side leg, a firebox bounded by said side legs and said basal legs, a compartment for each section which is positioned above the firebox and fluidically connected to the Side legs of said sections and to be partially or substantially completely filled with water, a tankless water heater coil heated by water in said compartment, a nipple port mounted in said boiler above the larger side legs, the heat emanating from the firebox to be directly supplied to said side legs and said basal legs and to the compartments and causing the water in the legs having the larger capacity to move downwardly while the water in the opposite legs moves upwardly.
 20. A boiler according to claim 19 in which the tankless water heater coil is mounted in said compartments.
 21. A boiler according to claim 19 in which the tankless water heater coil is mounted in the nipple port. 